The present invention relates to a system for controlling the fuel injection of an automotive engine in dependency on a throttle opening degree and engine speed.
In a known fuel injection system, a basic fuel injection pulse width Tp is calculated in dependency on throttle opening degree .alpha. and engine speed Ne. The basic pulse width Tp is stored in a table and is derived from the table for controlling the fuel injection during the operation of the engine.
At a transient state of the operation of the engine, the basic fuel injection pulse width Tp is corrected in dependency on various factors such as engine speed, pressure in an intake passage, coolant temperature and vehicle speed, so that air-fuel mixture is prevented from becoming rich or lean (see for example, Japanese Patent Laid Open Nos. 58-48720 and 58-41230).
However, since there is a space between the throttle valve and the cylidners of the engine, such as a chamber formed downstream of the throttle valve, changing of the actual amount of inducted air per engine cycle in response to the change of the throttle opening degree during the transient state is delayed. Accordingly, when the throttle valve is rapidly opened, the air-fuel mixture becomes rich. To the contrary, when the throttle valve is rapidly closed, the air-fuel ratio becomes lean.
In order to overcome such a defect, it is preferable to infer the quantity of the air inducted in the cylinder of the engine in one cycle in accordance with a model equation and to correct the basic injection pulse width based on the estimated quantity.